Bug with dashses in unquoted strings

The following query:

```
data.relationships.flow-actions.data[].id
```

is invalid syntax according to the specification, because dashes are not allowed in unquoted strings, however this library allows it. I guess we are missing a spec compliance test that asserts there's a parse error. FYI, the PHP implementation is correct, and rejects that input.

The origin of this report is https://github.com/jmespath/jmespath.php/issues/57#issuecomment-571821595.